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Article

Changes in Land Use Influenced by Anthropogenic Activity  

Lang Wang and Zong-Liang Yang

The terms “land cover” and “land use” are often used interchangeably, although they have different meanings. Land cover is the biophysical material at the surface of the Earth, whereas land use refers to how people use the land surface. Land use concerns the resources of the land, their products, and benefits, in addition to land management actions and activities. The history of changes in land use has passed through several major stages driven by developments in science and technology and demands for food, fiber, energy, and shelter. Modern changes in land use have been increasingly affected by anthropogenic activities at a scale and magnitude that have not been seen. These changes in land use are largely driven by population growth, urban expansion, increasing demands for energy and food, changes in diets and lifestyles, and changing socioeconomic conditions. About 70% of the Earth’s ice-free land surface has been altered by changes in land use, and these changes have had environmental impacts worldwide, ranging from effects on the composition of the Earth’s atmosphere and climate to the extensive modification of terrestrial ecosystems, habitats, and biodiversity. A number of different methods have been developed give a thorough understanding of these changes in land use and the multiple effects and feedbacks involved. Earth system observations and models are examples of two crucial technologies, although there are considerable uncertainties in both techniques. Cross-disciplinary collaborations are highly desirable in future studies of land use and management. The goals of mitigating climate change and maintaining sustainability should always be considered before implementing any new land management strategies.

Article

Machine Learning Tools for Water Resources Modeling and Management  

Giorgio Guariso and Matteo Sangiorgio

The pervasive diffusion of information and communication technologies that has characterized the end of the 20th and the beginning of the 21st centuries has profoundly impacted the way water management issues are studied. The possibility of collecting and storing large data sets has allowed the development of new classes of models that try to infer the relationships between the variables of interest directly from data rather than fit the classical physical and chemical laws to them. This approach, known as “data-driven,” belongs to the broader area of machine learning (ML) methods and can be applied to many water management problems. In hydrological modeling, ML tools can process diverse data sets, including satellite imagery, meteorological data, and historical records, to enhance predictions of streamflow, groundwater levels, and water availability and thus support water allocation, infrastructure planning, and operational decision-making. In water demand management, ML models can analyze historical water consumption patterns, weather data, and socioeconomic factors to predict future water demands. These models can support water utilities and policymakers in optimizing water allocation, planning infrastructure, and implementing effective conservation strategies. In reservoir management, advanced ML tools may be used to determine the operating rule of water structures by directly searching for the management policy or by mimicking a set of decisions with some desired properties. They may also be used to develop surrogate models that can be rapidly executed to determine the optimal course of action as a component of a decision-support system. ML methods have revolutionized water management studies by showing the power of data-driven insights. Thanks to their ability to make accurate forecasts, enhanced monitoring, and optimized resource allocation, adopting these tools is predicted to expand and consistently modify water management practices. Continued advancements in ML tools, data availability, and interdisciplinary collaborations will further propel the use of ML methods to address global water challenges and pave the way for a more resilient and sustainable water future.

Article

Politics of Water Flows: Water Supply, Sanitation, and Drainage  

Tatiana Acevedo Guerrero

Since the late 20th century, water and sanitation management has been deeply influenced by ideas from economics, specifically by the doctrine of neoliberalism. The resulting set of policy trends are usually referred to as market environmentalism, which in broad terms encourages specific types of water reforms aiming to employ markets as allocation mechanisms, establish private-property rights and full-cost pricing, reduce (or remove) subsidies, and promote private sector management to reduce government interference and avoid the politicization of water and sanitation management. Market environmentalism sees water as a resource that should be efficiently managed through economic reforms. Instead of seeing water as an external resource to be managed, alternative approaches like political ecology see water as a socio-nature. This means that water is studied as a historical-geographical process in which society and nature are inseparable, mutually produced, and transformable. Political ecological analyses understand processes of environmental change as deeply interrelated to socioeconomic dynamics. They also emphasize the impact of environmental dynamics on social relations and take seriously the question of how the physical properties of water may be sources of unpredictability, unruliness, and resistance from human intentions. As an alternative to the hydrologic cycle, political ecology proposes the concept of hydrosocial cycle, which emphasizes that water is deeply political and social. An analysis of the politics of water flows, drawing from political ecology explores the different relationships and histories reflected in access to (and exclusion from) water supply, sanitation, and drainage. It portrays how power inequalities are at the heart of differentiated levels of access to infrastructure.

Article

Review of the State of the Art in Analysis of the Economics of Water Resources Infrastructure  

Marc Jeuland

Water resources represent an essential input to most human activities, but harnessing them requires significant infrastructure. Such water control allows populations to cope with stochastic water availability, preserving uses during droughts while protecting against the ravages of floods. Economic analysis is particularly valuable for helping to guide infrastructure investment choices, and for comparing the relative value of so called hard and soft (noninfrastructure) approaches to water management. The historical evolution of the tools for conducting such economic analysis is considered. Given the multimillennial history of human reliance on water infrastructure, it may be surprising that economic assessments of its value are a relatively recent development. Owing to the need to justify the rapid deployment of major public-sector financing outlays for water infrastructure in the early 20th century, government agencies in the United States—the Army Corps of Engineers and the Bureau of Reclamation—were early pioneers in developing these applications. Their work faced numerous technical challenges, first addressed in the drafting of the cost-benefit norms of the “Green Book.” Subsequent methodological innovation then worked to address a suite of challenges related to nonmarket uses of water, stochastic hydrology, water systems interdependencies, the social opportunity cost of capital, and impacts on secondary markets, as well as endogenous sociocultural feedbacks. The improved methods that have emerged have now been applied extensively around the world, with applications increasingly focused on the Global South where the best infrastructure development opportunities remain today. The dominant tools for carrying out such economic analyses are simulation or optimization hydroeconomic models (HEM), but there are also other options: economy wide water-economy models (WEMs), sociohydrological models (SHMs), spreadsheet-based partial equilibrium cost-benefit models, and others. Each of these has different strengths and weaknesses. Notable innovations are also discussed. For HEMs, these include stochastic, fuzz, and robust optimization, respectively, as well as co-integration with models of other sectors (e.g., energy systems models). Recent cutting-edge work with WEMs and spreadsheet-based CBA models, meanwhile, has focused on linking these tools with spatially resolved HEMs. SHMs have only seen limited application to infrastructure valuation problems but have been useful for illuminating the paradox of flood management infrastructure increasing the incidence and severity of flood damages, and for explaining the co-evolution of water-based development and environmental concerns, which ironically then devalues the original infrastructure. Other notable innovations are apparent in multicriteria decision analysis, and in game-theoretic modeling of noncooperative water institutions. These advances notwithstanding, several issues continue to challenge accurate and helpful economic appraisal of water infrastructure and should be the subject of future investigations in this domain. These include better assessment of environmental and distributional impacts, incorporation of empirically based representations of costs and benefits, and greater attention to the opportunity costs of infrastructure. Existing tools are well evolved from those of a few decades ago, supported by enhancements in scientific understanding and computational power. Yet, they do appear to systematically produce inflated estimations of the net benefits of water infrastructure. Tackling existing shortcomings will require continued interdisciplinary collaboration between economists and scholars from other disciplines, to allow leveraging of new theoretical insights, empirical data analyses, and modeling innovations.

Article

Wastewater Reclamation and Recycling  

Soyoon Kum and Lewis S. Rowles

Across the globe, freshwater scarcity is increasing due to overuse, climate change, and population growth. Increasing water security requires sufficient water from diverse water resources. Wastewater can be used as a valuable water resource to improve water security because it is ever-present and usually available throughout the year. However, wastewater is a convoluted solution because the sources of wastewater can vary greatly (e.g., domestic sewage, agricultural runoff, waste from livestock activity, and industrial effluent). Different sources of wastewater can have vastly different pollutants, and mainly times, it is a complex mixture. Therefore, wastewater treatment, unlike drinking water treatment, requires a different treatment strategy. Various wastewater sources can be reused through wastewater reclamation and recycling, and the required water quality varies depending on the targeted purpose (e.g., groundwater recharge, potable water usage, irrigation). One potential solution is employing tailored treatment schemes to fit the purpose. Assorted physical, chemical, and biological treatment technologies have been established or developed for wastewater reclamation and recycle. The advancement of wastewater reclamation technologies has focused on the reduction of energy consumption and the targeted removal of emerging contaminants. Beyond technological challenges, context can be important to consider for reuse due to public perception and local water rights. Since the early 1990s, several global wastewater reclamation examples have overcome challenges and proved the applicability of wastewater reclamation systems. These examples showed that wastewater reclamation can be a promising solution to alleviate water shortages. As water scarcity becomes more widespread, strong global initiatives are needed to make substantial progress for water reclamation and reuse.

Article

Water Risks and Rural Development in Coastal Bangladesh  

Sonia Hoque and Mohammad Shamsudduha

Rural populations in river deltas experience multiple water risks, emerging from intersecting anthropogenic and hydroclimatic drivers of change. For more than 20 million inhabitants of coastal Bangladesh—living on the lower reaches of the Ganges–Brahmaputra–Meghna mega-delta—these water risks relate to access to safe drinking water, management of water resources for farm-based livelihoods, and protection from water-related hazards. To address these risks, water policies in the 20th century emphasized infrastructure development, ranging from embankments for flood protection to handpumps for rural water supply. However, interventions designed to promote aggregate economic growth often resulted in sociospatial inequalities in risk distribution, particularly when policy-makers and practitioners failed to recognize the complex dynamics of human–environment interactions in the world’s most hydromorphologically active delta. In Bangladesh’s southwestern region, construction of the polder system (embanked islands interlaced with tidal rivers) since the late 1960s has augmented agricultural production by protecting low-lying land from diurnal tidal action and frequent storm surges. However, anthropogenic modification of the natural hydrology, emulating the Dutch dyke system, has altered the sedimentation patterns and resulted in severe waterlogging since the 1980s. Contrary to their intended purpose of keeping saline water out, the polders also facilitated growth of export-oriented brackish water shrimp aquaculture, resulting in widespread environmental degradation and social inequalities from shifting power dynamics between large and small landholding farmers. Throughout the 1990s, there were several incidences of violent conflicts between the local communities and government authorities, as well as between different farmer groups. Waterlogged communities demanded to revert to indigenous practices of controlled flooding. Despite being formally adopted as a policy response, the implementation of tidal river management by the government has only been partially successful owing to bureaucratic delays, unfair compensation, and design flaws. Similarly, antishrimp movements gained momentum in several polders to ban the deliberate flooding of cropland with saline water. These narratives of conflict and cooperation demonstrate the complexities of policy outcomes, the unequal distribution of water risks, and the need to integrate local knowledge in decision-making. Social and spatial inequalities are also prevalent in access to safe drinking water owing to heterogeneity in groundwater salinity and infrastructure investments. Public investments are skewed toward low-salinity areas where tubewells are feasible, while high-salinity areas are often served by uncoordinated donor investments in alternative technologies, such as small piped schemes, reverse osmosis plants, and pond sand filters, and household self-supply through shallow tubewells and rainwater harvesting. These struggles to meet daily water needs from multiple sources pose uncertain and unequal water quality and affordability risks to coastal populations. The path-dependent sequences of infrastructure and institutional interventions that shaped the development trajectory of coastal Bangladesh exemplify the complexities of managing water risks and varied responses by public and private actors. While structural solutions still dominate the global water policy discourse, there is increased recognition of the nonlinearity of risks and responses, as well as the need to incorporate adaptive decision-making processes with room for social learning and uncertainties.